Soybean Stem Pests: Survey, Impact and Education
Sustainable Production
Crop protectionDiseaseField management
Lead Principal Investigator:
Jason Bond, Southern Illinois University at Carbondale
Co-Principal Investigators:
Ahmad Fakhoury, Southern Illinois University
Kelly Estes, University of Illinois at Urbana-Champaign
Nick Seiter, University of Illinois at Urbana-Champaign
Glen Hartman, USDA/ARS-University of Illinois
+3 More
Project Code:
Contributing Organization (Checkoff):
Brief Project Summary:
Researchers will survey farmers to see how they manage stem diseases and pests. The survey has not been conducted in nearly 20 years. The team will collect soybean plant samples themselves as well as from farmers and will use molecular techniques to confirm diseases. They are conducting an insect pest assessment with Illinois entomologists as well. A database will be developed on disease and pest ranges across the state and provide feedback to farmers as well.
Key Beneficiaries:
#agronomists, #entomologists, #farmers, #pathologists+G6
Unique Keywords:
#soybean diseases, #soybean pests
Information And Results
Project Summary

This proposed work aims to conduct a survey of important stem diseases and insect pests affecting soybean, identifying pests and assessing adopted management practices.

Proposal description – This proposed work aims to conduct a survey of important diseases and insects affecting soybean stems, identifying pathogens, and assessing adopted management practices. Stem diseases of soybean, including anthracnose stem blight, brown stem rot, charcoal rot, Phytophthora stem rot, stem blight, red crown rot, and stem canker, can cause significant loss in yield. According to disease loss estimates reported through the Crop Protection Network (https://cropprotectionnetwork.org/resources/publications/soybean-disease-loss-estimates-2018), stem diseases resulted in 257 million bushels lost. Moreover, in some instances, new diseases have been reported in some soybean production areas, or the identity of the specific pathogens that cause a particular stem disease is not resolved or is changing. For instance, Calonectria ilicicola, the pathogen that causes red crown rot was first identified in Illinois in 2018. 20-30 bu/a losses have been reported when the disease is severe. In a survey conducted in 2020, red crown rot was confirmed in 4 counties in Illinois, including St. Clair, Madison, Pike, and Sangamon (N. Kleczewski personal observation).

Stem canker is another problematic disease that affects yield in soybean. The estimated cumulative economic loss (1996 – 2016) attributed to stem canker in IL is $249 million (Bandara et al., 2020). Northern stem canker is caused by Diaporthe caulivora, while southern stem canker is caused Diaporthe aspalathi. The distribution of either pathogen in Illinois has not been entirely resolved. Moreover, both pathogens are part of the Diaporthe disease complex that also cause seed decay and stem and pod blight on soybean. Besides these two species, there are other Diaporthe species that cause stem canker, although their occurrence in Illinois is not known.

Brown stem rot, another disease affecting soybean stems, is believed to be widespread in Illinois from the central to the northern border. The symptoms and the extent of yield reduction in soybean due to brown stem rot depend on environmental conditions, the cultivar used, and the pathogen type. The reduction in number and size of seeds produced by infected plants may cause yield losses up to 30%. Yield reductions are greatest when wet and cool conditions prevail during the pod-fill stage, followed by hot, dry conditions. Two major subspecific types of the brown stem rot pathogen (Cadophora gregata) are known in the state that cause different symptom patterns, including one pattern that looks similar to the foliar phase of sudden death syndrome; both types can reduce yield. The occurrence of brown stem rot may be less frequent in central and southern Illinois, although the disease is known to occur in Georgia. The distribution throughout the state is not well documented.

Charcoal rot is another disease that affects soybean production across soybean production areas in the United States. Although the disease caused by the fungal pathogen Macrophomina phaseolina has historically been described as a “southern disease”, mainly associated with high temperatures and dry conditions, charcoal rot has been reported to cause losses in the Midwest and in Ontario, Canada. The wide host range of the pathogen and the limited resistance available in northern soybean cultivars stress the need to have a better assessment of the incidence of the disease in Illinois, the extent of yield loss in causes, the diversity in the population of the pathogen across the state, and the producers’ perceptions about the disease.

White mold (Sclerotinia stem rot) caused by the fungus Sclerotinia sclerotiorum is especially problematic in Northern production areas, as the disease is often associated with cool and wet conditions. The disease is characterized by the fluffy white growth of mycelia, often accompanied by the presence of black structures called sclerotia.

Several insects impact soybean production. We are proposing to investigate the impact of Dectes stem borer and the early detection of soybean gall midge on soybean production in Illinois.

Soybean farmers in southern Illinois have noted increased Dectes stem borer (Dectes texanus texanus) damage in recent years. Dectes stem borer larvae bore into the soybean stem; this injury can lead to lodging and, ultimately, yield loss when these larvae girdle the base of the stems as plants mature. The location of Dectes stem borer larvae within the stem makes scouting difficult, and they are often present in fields without causing lodging or yield loss. Furthermore, many factors not related to insect damage can also lead to soybean lodging at harvest time. As a result, the true extent of Dectes stem borer incidence and economic damage is poorly understood in Illinois.

Soybean gall midge (Resseliella maxima) is a new pest of soybean that has caused severe damage in eastern Nebraska and western Iowa. So far, this insect has been detected in five states, but not in Illinois (https://soybeangallmidge.org/soybean-gall-midge-distribution). A similar species was found feeding on white mold in Minnesota but did not cause damage to soybean. Early identification of soybean gall midge if and when it arrives in Illinois will be critical to developing management guidelines for this potential invasive pest. In addition, understanding the distribution of similar, non-damaging gall midge species (which have not been studied in Illinois) will help us avoid “false positive” reports that could distort the true impact of soybean gall midge

Project Objectives

Proposed methods/tactics – Infected samples will be collected across Illinois, and the main pathogenic species will be identified. The data will be summarized and used to increase awareness of stem diseases and insect pests of soybean in Illinois through various oral and written communications, including fact sheets that can be downloaded through the ISA website. This information will guide management strategies and identify future studies that may be needed to target the control of these stem diseases and insect pests.

Assessing the incidence and severity of diseases and insect pests and identifying the causing organisms are essential to develop and deploy tools to manage those diseases.

Our objectives in this proposal are to:
• Collect infected plant material from production fields across Illinois.
• Identify the main pathogen and insect species.

Project Deliverables

Producers, crop consultants, and researchers will be invited to identify soybean production fields with a reported incidence of stem diseases and insect pests and/or to collect plants with symptoms of stem diseases. This will be complemented with surveying for stem disease and insect pests and collecting diseased plant samples by the collaborators on this project. The collected samples will be processed in the collaborators’ laboratories in Carbondale and Urbana. Symptoms will be documented, and the pathogens and insect pests identified. The identity of the pathogens will be confirmed by microscopy and/or using specific molecular tools, including the amplification, and sequencing of specific fungal and oomycete DNA barcodes, mainly the Internal Transcribed Spacer (ITS) region and the Translation Elongation Factor 1 (TEF1) region.

The isolated and cultured fungal and oomycete species will be processed for mid- and long-term storage and added to existing collections of pathogens of soybean housed in the collaborators’ laboratories in Carbondale and Urbana.

Proposed outcomes – The proposed research will improve our understanding of stem diseases' perceived and actual impact on soybean production in Illinois. It will also help identify the major and most impactful pathogens that cause these diseases in IL.

More specifically, this proposed research will:

• Monitor the incidence and spread of red crown rot in Illinois. This will help elucidate the importance of this pathogen in Illinois and whether this disease is expanding in the state.

• Determine what fungal species cause stem canker in Illinois. This information is essential to manage the disease and use adequate management tools, including developing and deploying adequate sources of resistance to the pathogen.

• Assess the incidence and the potential yield loss caused by Dectes stem borer in soybean production fields in Illinois.

• Assess and survey Illinois soybean fields for the soybean gall midge with the purpose of early detection of this new soybean pest.

• Result in building a collection of pathogens associated with stem diseases. Such collections are an invaluable resource for researchers to study the biology of these pathogens. They also permit assessing host resistance under controlled conditions.

The information generated from the proposed research will be crucial to direct and prioritize future research targeting the management of the most destructive soybean stem-diseases-causing pathogens in Illinois.

Communications plan – This proposal's target audience includes soybean farmers, researchers, extension agents, and crop advisors. Research results will be summarized in quarterly reports. They will be distributed to the research and agricultural communities through scientific papers, extension publications posted on the Crop Protection Network, and presentations at scientific and farmer meetings. The data will also be shared with Illinois’ growers and crop advisors by collaborating with the ISA communication team. The produced data will be used to increase awareness of stem diseases of soybean in Illinois. The produced data will also help guide future studies targeting the management of those diseases.

Progress Of Work

Updated November 2, 2022:
Project update – In the first 7 months of the current project, fields were surveyed for stem diseases and pests. Forty-one fields were sampled for Dectes stem borer stem tunneling with help from farmer and crop advisor collaborators. Infestation levels ranged from 0-64% of stems infested with Dectes stem borer larvae. Stem diseases were surveyed in the fall in multiple counties with a total of 6 diseases found. Nearly all fields surveyed had Anthracnose and Diaporthe spp. The pathogens were isolated and their identity was confirmed by sequencing. We also developed the plans to survey fields during the 2022 growing season for sweep samples and visual surveys.

The farmer survey was developed and will be administered by ISA during late summer and early fall. We will use this information for informational products to alert farmers on the incidence of diseases and insect pests. The results of the survey will be compared to the data that we are generating from the samples that we are collecting. The results will also guide the researchers as we develop better management options to protect stem health.

Final Project Results

Benefit To Soybean Farmers

The produced data will be used to increase awareness of stem diseases of soybean in Illinois. The produced data will also help guide future studies targeting the management of those diseases.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.